The present invention relates to film carrier tapes, especially, to film carrier tapes used in a tape carrier bonding (Tape Automated Bonding) process and methods of evaluating the film carrier tapes.
Conventional film carrier tapes have a plurality of lead terminals with an end thereof being connected to a semiconductor chip and the other end being provided with an electrical sorting (screening) pad.
FIG. 13 is a schematic plan view showing a conventional film carrier tape. An insulating film 100 has sprocket holes 102 formed along both sides thereof for transport and positioning purposes. Also, the insulating film 100 has in the middle thereof semiconductor chip mounting holes 104 where semiconductor chips are mounted. Further, the insulating film 100 is provided thereon with a plurality of lead terminals 106 each extending over the semiconductor chip mounting hole 104 at one end thereof, while an electrical sorting pad 108 is formed at the other end of each of the lead terminals 106.
Demands on the semiconductor chip for higher integrity and high performance in recent years have resulted in the semiconductor chip having more input and output terminals (bonding pads on the semiconductor chip) and hence more lead terminals 106. Therefore, the pitches are decreasing between the lead terminals 106. As a result, the pitches between the lead terminal 106 of a film carrier tape are in some cases smaller than the smallest pitch required to provide the electrical sorting pad 108.
Therefore the electrical sorting pads 108 of such a film carrier tape are configured as shown in FIG. 14 for example: the electrical sorting pads 108 are disposed along a zigzag line.
However, the region of the insulating film (not shown) where the electrical sorting pads 108 are formed is unnecessary and cut off along line IIIxe2x80x94III shown in FIG. 14 when the semiconductor chip is mounted on the insulating film. The zigzag configuration of the electrical sorting pads 108 shown in FIG. 14 increases the area of the region of the insulating film where the electrical sorting pads 108 are formed. In other words, a larger portion of the insulating film is wasted. This results in less packages (semiconductor chips) being mounted on the film carrier tape, and hence higher production costs. Besides, the tester cannot be equipped with an enough number of lead probes (measurement terminals) to match the increased number of the electrical sorting pads 108.
To solve these problems, FIG. 15 suggests a film carrier tape of which adjacent lead terminals 106 share a single electrical sorting pad 108.
The film carrier tape having such electrical sorting pads 108 can accommodate more lead terminals 106 without additional electrical sorting pads 108; thereby a smaller portion of the insulating film 100, which will be cut off along line IVxe2x80x94IV shown in FIG. 16, is wasted. Apart from that, the film carrier tape uses a smaller number of electrical sorting pads 108 and can be configured so that the number of the electrical sorting pad 108 matches the number of lead probes of a conventional tester.
However, with the film carrier tape shown in FIG. 16, a short circuit cannot be detected which possibly occurs between adjacent lead terminals 106 that commonly share an electrical sorting pad 108.
To solve those problems, Japanese Laid-Open Patent Application No. 6-104316/1994 (Tokukaihei 6-104316, published on Apr. 15, 1994) discloses a film carrier tape shown in FIG. 17. The film carrier tape has lead terminal groups each consisting of one or more lead terminals 106, and a common electrical sorting pad 108 is formed for each lead terminal group. This configuration enables detection of short circuits between adjacent lead terminals 106.
However, the film carrier tape shown in FIG. 17 disenables the detection of broken conductivity of the lead terminal 106 belonging to a lead terminal group when a delivery inspection (an inspection before delivery of the film carrier tape from the production line) is conducted in the manufacturing process of the film carrier tape on which no semiconductor chip is yet mounted.
FIG. 18 shows an example of delivery inspection conducted in the manufacturing process of the film carrier tape to detect a broken lead terminal 106. In the delivery inspection, the lead terminals 106, extending over the semiconductor chip mounting hole 104, are caused to commonly contact an electrode plate 110, whereas the electrical sorting pads 108 are caused to contact the lead probes 112 of a tester. A broken lead terminal 106 is detected by the securing card 114 of the tester confirming electrical conductivity between the lead probes 112 to the electrode plate 110.
The tester therefore comes short of detecting the broken lead terminal 106 belonging to the lead terminal group shown encircled by broken lines in FIG. 19 for example, since the electrical sorting pad 108 of that lead terminal group is electrically connected to the electrode plate 110 as long as the other lead terminal 106 of the same lead terminal group is in good conditions. The film carrier tape thus passes the delivery inspection, and the defect is not found until an electrical sorting process after semiconductor chips are mounted, which inevitably leads to greater production cost.
The present invention has an object to offer film carrier tapes, and methods of evaluating thereof, capable of curbing increase in production cost that would otherwise results from increased use of film materials and reducing the number of measurement terminals required by a tester used for an inspection after the mounting of semiconductor chips as well as detecting all broken lead terminals in a delivery inspection conducted in the manufacturing process of the film carrier tapes.
In order to accomplish the above object, the film carrier tape in-accordance with the present invention includes:
a plurality of lead terminals that are each disposed on an insulating film and provided with an end connected to a semiconductor chip and another end having an electrical sorting pad,
wherein the electrical sorting pads of two or more of the plurality of lead terminals that are not adjacent to one another are electrically separated from one another and configured so that electrical sorting can be simultaneously conducted thereon through the two or more of the plurality of lead terminals.
With the above arrangement, in a delivery inspection to detect broken conductivity of a lead terminal which is conducted in the manufacturing process of a film carrier tape before a semiconductor chip is mounted, an electrode plate or the like is caused to commonly contact the ends of the lead terminals which will be connected to the semiconductor chip. Subsequently, electric connection (conductivity) is confirmed between the electrode plate and the electrical sorting pads provided at the other ends of the lead terminals to detect broken conductivity of each lead terminal individually.
If the film carrier tape is such that two or more lead terminals share a single electrical sorting pad, those lead terminals are connected electrically parallel to one another between the electrical sorting pad and the electrode plate. The parallel configuration of the lead terminals allows conductivity to be detected between the electrical sorting pad and the electrode plate even if one or some of the parallel lead terminals is/are broken. In other words, broken conductivity is not detected unless all the lead terminals are broken. In such a case, the film carrier tape passes the delivery inspection, and the defect is not found until an electrical sorting process after a semiconductor chip is mounted, which inevitably leads to greater production cost.
To tackle the problems, according to the present invention, the electrical sorting pads of two or more of the lead terminals that are not adjacent to one another are configured so as to allow a broken conductivity inspection to be conducted on each lead terminal individually. Therefore, the lead terminals are not connected electrically parallel to one another between the electrical sorting pad and the electrode plate. Hence, if at least one lead terminal is broken among the two or more of the lead terminals that are not adjacent to one another, conductivity is not detected, i.e., broken conductivity is detected.
After a semiconductor chip is mounted, electrical sorting is conducted on the lead terminals. With the foregoing arrangement, the electrical sorting pads of two or more of the lead terminals that are not adjacent to one another are configured so that electrical sorting can be simultaneously conducted thereon through those lead terminals. Therefore, electrical sorting can be simultaneously conducted on the electrical sorting pads through the lead terminals. The electrical sorting pads thus function as a single electrical sorting pad. This is in practice equivalent to a reduction in the number of electrical sorting pads, and allows a reduction in the number of measurement terminals of a tester used in an electrical sorting process after the mounting of a semiconductor chip. Also, this holds down expansions of the area in which electrical sorting pads are disposed, and thereby effectively avoids increased production cost which would be otherwise caused by increased use of material of the insulating film.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.